1. Field of the Invention
The present invention relates to a tool and method for cleaning deposits, scale and other buildup on the inside surfaces of pipelines.
2. Description of the Prior Art
Petroleum, geothermal, sewage, and other pipelines utilized to conduct fluids often develop buildups of deposits, scale, and other materials on the inner wall surfaces of the pipes that make up the pipeline. Continued buildup of accretions on the walls of a pipeline reduces the volume of fluid that flows through the pipeline and increases the resistance to flow through the line. Eventually the opening through the center of the pipeline decreases in cross-sectional area to such a degree that cleaning of the pipeline is imperative in order for it to continue to be useful for the conduction of fluids.
In conventional practice, maintenance to unclog pipelines in which clogging deposits can be scoured by water alone may be performed by creating an opening in a pipeline and inserting a cleaning hose into the opening. The hose is directed toward a remote end of the section of pipeline to be cleaned. A cleaning liquid ejection nozzle is located at the end of the pipeline cleaning hose and is equipped with jets that are directed rearwardly back from the end of the hose. To clean the pipeline, the operative end of the cleaning hose that bears the jetting nozzle is inserted through the pipeline opening and into the pipeline. Water under pressure is then pumped through the hose. This water is emitted from the rearwardly directed jets at the operating end of the cleaning hose from the cleaning ejection nozzles. The water discharged through the jets is thereby directed back along the pipeline toward the opening through which these cleaning hose is inserted.
The jets of water under pressure ejected from the hose nozzle serve to propel the operating, ejection end of the cleaning hose further along the pipeline, away from the opening. Also, the jets scour the walls of the pipeline as the operating end of the hose is propelled along the pipeline. The pipeline cleaning hose is wound on a large hose spool or reel located near the opening in the pipeline. As the operating end of the cleaning hose propels itself along the pipeline, additional lengths of cleaning hose are fed off of the reel to permit the operating end of the cleaning hose to continue to travel along the pipeline, going ever further from the access opening.
In other situations the nature of the buildup on the interior walls of the pipeline is such that the application of water pressure alone is entirely inadequate to dislodge the accumulated build up. For example, the buildup of minerals and compounds on the inside of pipelines used in geothermal applications can rarely be removed by water pressure alone. A much heavier-duty pipeline cleaning system is required in such situations.
One conventional heavy-duty pipeline cleaning system that is currently in use to clean geothermal pipelines is operated by EP and Associates, located in California. This system involves a tool having a plurality of notched discs of increasing diameter mounted on its forward, or downstream end, and also radially outwardly directed rollers also located on the downstream end. On its upstream end the EP and Associates"" tool employs a steel disc that has a plurality of short fingers or fins located about its periphery. This disc with its hinged fingers provides a backing for a disc-shaped Kevlar(copyright) seal located upstream therefrom.
The EP and Associates"" pipeline cleaning tool also has significant operating problems. It requires a very high operating pressure, typically between five hundred and six hundred pounds per square inch of water to exert a force against the upstream surface of the Kevlar(copyright) disc to propel the tool through the pipeline. Also, this tool is subject to extreme damage as it advances through a clogged pipeline. It can typically be utilized to clean only about six hundred linear feet of a fourteen inch diameter pipeline before it must be rebuilt. Also, the pipeline has to be cut frequently since the tool becomes so degraded that it will not travel far before becoming hopelessly lodged in a pipeline having a heavy build up of clogging accretions.
The present invention involves a rugged pipeline cleaning tool that is constructed quite differently from prior pipeline cleaning tools and which has very important operating advantages. The pipeline cleaning tool of the present invention, like the EP and Associates"" tool, is propelled by the application of water pressure to the upstream sealing face of the tool. Unlike the EP and Associates"" tool, however, the pipeline cleaning tool of the invention requires an operating water pressure about 120-180 psi. This reduction in water pressure is possible due to the unique construction of the folding propulsion system. Furthermore, the pipeline cleaning tool of the invention can clean over two thousand feet of clogged, twenty inch diameter pipe before requiring any refurbishment of components. Also, the pipeline cleaning tool of the invention is able to clean pipe throughout a much greater range of diameters without requiring disassembly and reassembly of different components than has heretofore been possible. Moreover, when it is necessary to install larger diameter components on the tool, the disassembly and reassembly process takes only about ten minutes.
The pipeline cleaning tool of the invention is relatively simple in construction, yet is highly durable. Also, it requires far less time and manpower to operate than conventional pipeline cleaning tools.
In one broad aspect the invention may be considered to be a pipeline cleaning tool comprising: an elongated support member; a rigid cutting unit; a folding propulsion assembly; a rotation limiting barrier; and a backing seal. The elongated support member has opposing first and second ends. The rigid cutting unit has a periphery, preferably with cutting teeth thereon, and is secured proximate the first end of the support member. The cutting unit projects radially outwardly from the support member. The folding propulsion assembly includes a hub, a plurality of sector panels, and expansion flaps. The hub is secured to the support member proximate the second end thereof. The sector panels are arranged about the periphery of the hub and are each hinged separately thereto for rotation independently of each other about axes tangentially oriented relative to the periphery of the hub. Each of the sector panels has opposing upstream and downstream faces and first and second side edges. The side edges of the sector panels diverge radially outwardly from each other. In this way the sector panels fan radially outwardly from the hub and define gaps therebetween.
An expansion flap is provided for each of the sector panels. The expansion flaps extend the lengths of the first side edges of the section panels and are hinged thereto. In this way the expansion panels bridge the gaps and overlap portions of the upstream faces of the sector panels immediately adjacent the sector panels to which they are hinged. The rotation limiting barrier is anchored to the elongated support member to prevent rotation of the sector panels past the hub in one direction of rotation relative thereto, and to permit free rotation of the sector panels relative to the hub in an opposite direction relative thereto. The backing seal is a disc-shaped structure formed of a flexible, water impervious material and anchored to the elongated support member on a side of the hub opposite the rotation limiting barrier.
The cutting unit may be formed of a flat, disc-shaped metal plate serrated at its outer periphery to form radially projecting cutting teeth. In many instances it is necessary to propel the cleaning tool of the invention through a section of pipe to be cleaned several times if the build up on the interior pipe wall is quite hard. This is because only a portion of the buildup can be removed in a single pass. When several passes of the tool through the pipeline are necessary, a serrated metal cutting disc of increased diameter can be substituted for the serrated disc employed in the previous pass in order to increase the central opening cleared by the tool with each successive pass through the section of pipeline to be cleaned.
In an alternative arrangement, the rigid cutting unit may have an adjustable cutting diameter. One way of making the diameter of the cutting unit adjustable is to form the unit with a pair of cutter element mounting discs mounted coaxially relative to the support member. Each of the cutter elements mounting discs has a plurality of angularly spaced mounting openings defined therethrough near its periphery. The mounting openings in the mounting discs are radially and longitudinally aligned with each other.
A plurality of flat cutting elements are located between the mounting discs and project radially outwardly therefrom. Each cutting element has a relatively wide outer end with cutting teeth defined at the outer periphery thereon and a relative narrow inner end with a radially elongated mounting opening defined therethrough. Clamping bolts extend through the mounting openings to hold the cutting elements firmly in place between the mounting discs. The cutting elements thereby project radially outwardly from the mounting discs an adjustable, selected distance from the elongated support member.
In another aspect the invention may be considered to be a pipeline cleaning tool comprising: an elongated central shaft having opposing first and second ends; a rigid cutting unit secured proximate the first end of the shaft; a propulsion unit secured proximate the second end of the shaft; a rotation barrier anchored to the shaft; and a backing seal.
The cutting unit extends radially outwardly from the shaft and preferably defines cutting teeth at its radial periphery. The propulsion units includes: a solid hub secured proximate the second end of the shaft; a plurality of sector panels projecting radially outwardly from the hub; and a separate expansion flap for each of the sector panels. The sector panels are independently hinged to the hub for rotation about axes tangential to the hub. Each of the sector panels has radially outwardly diverging first and second side edges. The expansion flaps are hinged for independent rotation along the first side edges of the sector panels.
The rotation barrier projects outwardly radially beyond the hub. The rotation barrier limits rotation of the sector panels relative to the hub toward only one of the ends of the shaft. The expansion flaps slide in overlapping contact with adjacent sector panels when the sector panels rotate toward the shaft and away from the one end of the shaft toward which the rotation barrier limits rotation. Together the hub, the sector panels, the expansion flaps, and the backing seal present a transverse obstruction in the pipeline to fluid flow past the shaft in a single longitudinal direction relative thereto.
In still another aspect the invention may be considered to be a method of cleaning a section of pipeline having an interior bounded by a cylindrical annular wall upon which clogging deposits have formed. The method of the invention utilizes a pipeline cleaning tool of the type previously described. The method is comprised of several steps. First, openings are formed in the pipeline at both ends of the section of pipeline to provide access to the interior thereof. The pipeline cleaning tool is then inserted into the interior of the pipeline at one of the openings at one of the ends of the section of pipeline. The end of the pipeline section into which the tool is inserted may be considered to be the upstream end of the pipeline section. The cleaning tool is inserted into the upstream end so that the upstream faces of the sector panels face the upstream end of the pipeline section.
Fluid is forced under pressure into the upstream end of the section of pipeline so that the fluid exerts a force against the upstream faces of the sector panels and against the expansion flaps. This tends to rotate the sector panels outwardly toward the annular wall of the pipeline section to form a pressure differential on opposite sides of the backing seal. The pressure differential propels the pipe cleaning tool toward other end of the pipeline section. The teeth of the cutting unit dislodge the clogging deposits from the annular wall of the pipeline section as the tool travels along the length of the section. The pipeline cleaning tool is removed from the other of the openings in the pipeline.
In some circumstances the cleaning tool must be passed through the pipeline section several times in succession. In such circumstances the cutting unit employed preferably has an adjustment mechanism for varying the distance at which the teeth are held from the support member. When the cleaning is complete, the openings in the pipeline are closed.
The invention may be described with greater clarity and particularity with reference to the accompanying drawings.